Communication networks typically operate in accordance with a given standard or specification which sets out what the various elements of the network are permitted to do and how that should be achieved. For example, the standard may define whether the user or more precisely, user equipment is provided with a circuit switched service or a packet switched service. The standard may also define the communication protocols which shall be used for the connection. The given standard also defines one or more of the required connection parameters. The connection parameters may relate to various features of the connection. The parameters may define features such as the maximum number of traffic channels, quality of service and so on. Features that relate to multi-slot transmission may also be defined.
In other words, the standard defines the “rules” and parameters on which the communication within the communication system can be based. Examples of the different standards and/or specifications include, without limiting to these, specifications such as GSM (Global System for Mobile communications) or various GSM based systems (such as GPRS: General Packet Radio Service), AMPS (American Mobile Phone System), DAMPS (Digital AMPS), WCDMA (Wideband Code Division Multiple Access) or CDMA in UMTS (Code Division Multiple Access in Universal Mobile Telecommunications System) and so on.
The user equipment i.e. a terminal that is to be used for communication over a particular communication network has to be implemented in accordance with the predefined “rules” of the network. A terminal may also be arranged to be compatible with more than one standard or specification, i.e. the terminal may communicate in accordance with several different types of communication services. These user equipment are often called multi-mode terminals, the basic example thereof being a dual-mode mobile station.
A communication network is a cellular radio network consisting of cells. In most cases the cell can be defined as a certain area covered by one or several base transceiver stations (BTS) serving user equipment (UE), such as mobile stations (MS), via a radio interface and possibly connected to a base station subsystem (BSS). Several cells cover a larger area, and form typically a radio coverage area referred to as a location area (LA) or in some standards as a routing area (RA). It should be appreciated that the size of the location area or routing area depends on the system and circumstances, and may equal to one cell or be even smaller, such a part of a coverage area of a base station. A feature of the cellular system is that it provides mobility for the mobile stations, i.e. the mobile stations are enabled to move from a location area to another, and even from a network to another network that is compatible with the standard the mobile station is adapted to.
The user equipment (UE) within one of the cells of the cellular system can be controlled by a node providing controller function. Examples of the controller nodes include a base station controller (BSC) and a radio network controller (RNC). The controller can be connected further to a gateway or linking node, for example a gateway GPRS support node (GGSN) or gateway mobile switching center (GMSC), linking the controller nodes to other parts of the communication system and/or to other communication networks, such as to a PSTN (Public Switched Telecommunications Network) or to a data network, such as to a X. 25 based network or to a TCP/IP (Transmission Control Protocol/Internet Protocol) based network. The network may also include nodes for storing information of mobile stations subscribing the networks or visiting the networks, such as appropriate home location registers (HLR), visitor location registers (VLR) and home subscriber servers (HSS).
A proposal for the developed communication systems comprises a third generation partnership project (3GPP) long term evolution (LTE) packet-switched only access scheme. In a proposed 3GPP long term evolution (LTE) access scheme, a flat architecture is provided by an evolved Node B (eNB) and an access Gateway (aGW) that are involved in controller functions. 3GPP is also performing a feasibility study associated with streamlining the 3GPP packet switched network architecture to be used for the access.
In the uplink (UL) part of a such communications system, reference signal sequences are transmitted between a user equipment (UE) and a network element or node. However, a problem still to be adequately addressed is how to enable reference signal transmission with sufficient orthogonality between the reference signals of multiple user equipments in a certain cell or in multiple cells. In particular, there is a need to improve the pilot signal's resistivity against intra- or intercell interference.